I FOUND THE ANSWER!!!
Here it IS!!!Aug 16, 2012 2:48 PM
When I bought my iPad it worked perfectly then all of a sudden after long time of usage the audio sounds of apps any kind of apps disappeared but the speakers still work because there are sounds on YouTube I don't know what to do I tried to upgrade the system but nothing changed please please helpiPad 2This solved my question by Demo on Aug 16, 2012 2:49 PM
If you lose sounds for keyboard clicks, games or other apps, email notifications and other notifications, system sounds may have been muted.
System sounds can be muted and controlled two different ways. The screen lock rotation can be controlled in the same manner as well.
Settings>General>Use Side Switch to: Mute System sounds. If this option is selected, the switch on the side of the iPad above the volume rocker will mute system sounds.
If you choose Lock Screen Rotation, then the switch locks the screen. If the screen is locked, you will see a lock icon in the upper right corner next to the battery indicator gauge.
If you have the side switch set to lock screen rotation then the system sound control is in the task bar. Double tap the home button and in the task bar at the bottom, swipe all the way to the right. The speaker icon is all the way to the left. Tap on it and system sounds will return.
If you have the side switch set to mute system sounds, then the screen lock rotation can be accessed via the task bar in the same manner as described above.
This support article from Apple explains how the side switch works.
The bit in BIGGER and italics is the answer, at least for me.
I'm not sure how mine ended up all muted...but pushing the home button 2x to get that task bar,(which I didn't even know about, and I've had the thing since month 1, orginal model), fixed it, IMMEDIATELY. There's also brightness control on that tyask bar.
The answer is simpler that that. Goto Settings/ General/
3/4 down the page You will come to a heading labelled
Switch slide to
There are 2 choices and 'Mute' and 'Lock Rotation ' make sure there that the check mark is beside Lock Rotation!
( it worked for me, so I realize that it is possible that yours won't work, or that there are other options)
Same thing here, this on a new iPad right out of the box. I found out the solution though all you have to do is set the rocker to change volume on sound effects and ringtones. It should be the first option under sound in settings. Set it to on, then try adjusting the volume and try the keyboard. Also make sure that both keyboard and lock screens aren't mute. You can set the rocker back to changing the volume to media and such by switching it back to off. Both keyboard and lock sounds returned after that. Hope that helps.